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Victoria University Antarctic Research Expedition Science and Logistics Reports 1993-94: VUWAE 38

Logistic operation and constraints

Logistic operation and constraints

The first part of the programme, to core from the fast ice at about 10 sites in Granite Harbour, would not only provide near shore scientific data but also a safe and stable platform from which to gain experience with the corer before ship deployment, with the considerable time pressures involved, in subsequent seasons. The party moved equipment and personnel with a D5 bulldozer, 2 five tonne cargo sledges, a sledge mounted accommodation/ laboratory wannigan, a steel sledge and a RN75 Nodwell vehicle with HIAB crane for lifting and drilling ice holes. This mode of operation has been used successfully for some years, and allows about 3 weeks field time after getting to Antarctica, testing equipment at Scott Base, travelling to the site and returning by around December 6, when summer warming cracks the sea ice.

The style of operation constrained the concept and design of the corer, putting a premium on lightness to reduce weight for the cargo sledges and for air cargo to and from Antarctica. Also because the equipment was developmental and had potential uses in back in New Zealand it was not considered feasible to send it to Antarctica the previous season by ship so it had to be air transported at the beginning of the season.

For operation from the fast ice up to 2.5 m thick the vibracorer needed to fit down a reasonably small hole, say 1.5 m in diameter. Also it was designed to operate from batteries to avoid an expensive and heavy power umbilical and large generator (15-20 KVA?) at the surface. It weighed 1.6-1.8 tonne in air and 1.2-1.5 tonne in water, though the exact weight is not known because of modifications to the legs in early 1993.

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The winch was designed to have a line pull of 2-2.5 tonne and again be kept as light as possible. It was powered from the Power Take Off of the hydraulic system on the Nodwell tracked vehicle. The line chosen was a polyester 20 mm diameter double braid rope with a breaking load of 7.5 tonne driven by a capstan onto a separately driven take up drum. A thimble eye splice at the end reduced the breaking load to 90% of the rated value, down to 6.75 tonne. With the corer weighing a maximum in water of 1.5 tonne the safety factor is 4.5. Polyester rope is low stretch and has the best resistance to UV, freezing temperatures and abrasion of the commonly used synthetic fibres.